/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/
function tongBn(val) {
    let p = new Promise((resolved, reject) => {
        setTimeout(() => {
            resolved(val + ' ')
        }, 10);
    })
    return p
}
tongBn().then(() => {
    return tongBn('hello');
}).then((val) => {
    return tongBn(val + 'lagou');
}).then((val) => {
    return tongBn(val + 'I ♥ U');
}).then((val) => {
    console.log(val);
});